Cerebral palsy (CP) is a central motor disorder caused by prenatal or perinatal damage to the immature brain and is often associated with other impairments such as mental retardation, epilepsy, and visual and auditory impairments. Among them, visual impairment is a common and important combined injury in cerebral palsy, which has a negative impact on the early motor development and later cognition of children with cerebral palsy. The importance of visual impairment, proper evaluation of visual function, as part of the rehabilitation program, and active promotion of the recovery and improvement of visual function play a very important role in the overall rehabilitation of children with cerebral palsy. This article will provide a review of visual impairment in children with cerebral palsy.
Visual impairment in cerebral palsy can occur in any part of the anterior or posterior visual pathway, including the lens, choroid, retina, and optic nerve in the anterior visual pathway; the occipital lobe, parietal cortex and other subcortical structures associated with vision, basal ganglia, thalamus, and even the frontal lobe in the posterior visual pathway. Visual disorders occurring in the anterior visual pathway include cataract, chorioretinitis, retinopathy, optic nerve atrophy, and macular degeneration.
The causes of their damage are infections, congenital diseases, etc., as in the case of sports injuries, and the incidence is not high. The more common visual impairment is damage to the optic pathway behind the optic cross and other brain areas related to perception and visual stimulus processing. Clinical findings of reduced visual function due to ocular abnormalities can exceed the findings of abnormal ophthalmologic examinations. Many studies have shown that even in the absence of ophthalmologic abnormalities, children with brain damage can have abnormal visual function; therefore, in recent years, this temporary or persistent visual impairment caused by posterior visual pathway disorders has been referred to as cerebral visual impairment.
Available epidemiological data show that the prevalence of visual defects in children with cerebral palsy is about 5% in retrospective analysis, and the incidence of severe visual impairment is about 8.9% in Pharoah POD et al. The latest information is 9.6%. It is evident that the actual incidence is higher than 5%.
I. Eye abnormalities
Common ocular abnormalities in children with cerebral palsy stemming from brain injury include strabismus, nystagmus, poor visual acuity, reduced visual field, and optic nerve atrophy. Strabismus is the most common manifestation, and is a common strabismus, with internal, external or superior strabismus. Strabismus in turn is often the cause of amblyopia. In China, Cao Jianguo reported a strabismus incidence of 20.52%, and Pennefanther et al. reported 51.9%, mostly seen in spastic biparesis (double paralysis). The pathological basis of strabismus is damage to the posterior optic pathway of the optic cross.
Seidl Z et al. reported MRI of a group of children with diplegia showing bilateral occipital angle enlargement, 16/18 had strabismus, and MRI showed white matter damage in the occipital region in all strabismic individuals.Jacobson et al. suggested that the immature visual system is susceptible to adverse events and that periventricular white matter softening (PVL) caused by ischemia and hypoxia impairs visual radiation as the underlying cause of visual impairment.PVL-induced Cerebral visual impairment is characterized by delayed visual maturation, low visual acuity, crowding phenomenon, visual field deficits and visual perception cognitive problems.MRI shows brain damage associated with optic papillary abnormalities, strabismus, nystagmus and optomotor impairment.
Reduced visual acuity is another important abnormality in cerebral palsy, and Schenk-Rootliet et al. reported that 70% of children with cerebral palsy had visual acuity below the normal range in both eyes, and that ophthalmologic findings could not explain the low visual acuity. Therefore, it is very likely that cerebral visual impairment is the cause. The degree of reduced visual acuity is related to the type of cerebral palsy, with hemiplegia being the best and tetraplegia the worst.
The most severe is blindness, and cerebral blindness is clearly associated with tetraplegia, as well as with the severity of visual radiation, visual cortex damage, level of intelligence, gross motor, and degree of oculomotor impairment as revealed by MRI. Poor visual acuity is often associated with other visual disorders such as strabismus and motor nystagmus. Abnormal visual acuity is associated with the type of cerebral palsy, commonly tetraplegia, dystonia, and to a lesser extent, diplegia. Those with hemiplegia generally have normal visual acuity. The degree of reduced visual acuity in children with diplegia has been reported to correlate with the findings of MRI. Visual field deficits are mainly associated with the primary visual cortex of the occipital lobe. Nystagmus is often associated with other visual disturbances, and nystagmus is common in PVL, mostly horizontal.
Oculomotor disorders
In a recent study of a group of children with dystonic cerebral palsy, Jan et al. found that in addition to visual impairments such as strabismus and nystagmus, they also had difficulty with random eye sweep, fixation, and gaze pursuit. When relaxed, visual function improves, but decreases during illness, sleepiness, agitation, fatigue or stress, and has difficulty controlling eye movements. In severe cases, it can also manifest as blindness and lead to misdiagnosis. Therefore, it is believed that there is a dystonic oculomotor disorder as well as a gross motor one.
Fedrizzi et al. studied oculomotor disorders in children with diplegia due to immaturity. It was measured with the Wechsler IQ or Griffiths developmental scale. Excluding those with verbal IQ or developmental quotient of 80 or less, excluding those with upper limb motor dysfunction, excluding dystonia and poor distance discrimination. Oculomotor parameters, including completion time, omission, scanning, sweeping and directional sequence completion, were recorded for completion of the animal house matching task, all of which were poorer than in the control group. Children with cerebral palsy took longer to complete the task, had a higher number of omissions, and had a lower ability to apply random sweeping movements, independent of age and related to the degree of brain damage.
III. Visual perceptual impairment
In recent years, many studies have been found to confirm the presence of visual perception impairment in children with cerebral palsy. vrie et al. studied neonatal PVL with ultrasound and VEP and infancy with MRI, and the results suggested that extensive cystic white matter softening was associated with later sensory impairment. flodmark et al. studied PVL with MRI showing a reduction in occipital, parietal, peri-triangular and optic radiating white matter in children with diplegia. The visual perceptual impairment was significantly correlated with the amount of reduction in peri-triangular white matter, the degree of posterior horn enlargement, and the thinning of the posterior corpus callosum in PVL. However, it has also been suggested that the absence of peri-triangular white matter is nonspecific.
Hood and Atkinson noted that children with neurological damage who have a fixed central target may show a lack of visual perceptual manipulation due to difficulties in moving gaze to peripheral targets. In some children with parietal lobe damage, abnormal fixation movements are often not associated with visual pursuit or sensory deficits. Impairment in shifting attention to the periphery and processing multiple targets may also be a major factor in the visual perceptual deficits of children with diplegia. This may be due to damage to the delta involving the connection pathway between the striatum and the parietal cortex.
Fedrizzi et al. found that the expected lack of sweeping eye movements in children with diplegia is not only a lack of visual perception, but may reflect deficits in sweeping eye movement coordination, attention to spatial location selection, or sensory integration development. The degree of impairment was not related to visual acuity and resulted from motor deficits caused by prenatal or perinatal brain injury. In children with normal ophthalmologic examination, optic radiations and visual cortex but abnormal visual function, it is possible that other parts of the brain, rather than the geniculo-striatal pathway, such as frontal or temporal lobe damage, are involved, which is related to visual attention or other visual functions.
Impairment of visual perception is not only caused by impaired visual pathways and impaired visual input due to PVL, but is also associated with oculomotor deficits due to visual output.
IV. Visual impairment and development
Studies have demonstrated that cerebral visual impairment is related to pediatric neurodevelopment. Vision plays a fundamental role in the motor, cognitive and emotional development of children. The effects of severe visual impairment on motor behavior are closely related and complex during the developmental stages of the child, and can cause impairment in all aspects of development.
New perspectives on motor development emphasize the role of central responses elicited by various sensory afferents, particularly visual perception, in motor development and postural control. The primary form of sensory access available to normal infants is visual, and vision has a very important role in the early stages of motor development. When the child acquires head or trunk control, he or she relies heavily on visual information in the sitting or standing position, and when postural control matures, the dominant role of vision disappears and the child begins to be able to integrate multiple sensory afferents. When learning new motor and postural control skills, children with cerebral palsy act like normal children. It is hypothesized that the impairment in achieving normal postural control adaptation in children with cerebral palsy is related to a strong dependence on sensory maintenance.
Children with cerebral palsy lack sensory organization in the mechanisms of postural control. In one study, children were asked to stand on a stable or rocking pedal and had difficulty adapting to changing states in the presence and absence of visual information. Children with cerebral palsy also have difficulty when integrating multiple sensory afferents.
Eken et al. found that neurodevelopmental scores and grating visual acuity were consistent in children with perinatal brain injury, and Mercuri Eugenio et al. studied the relationship between visual function and neurodevelopment at 2 years of age in term infants with ischemic hypoxia and found that multiple visual function abnormalities were significantly associated with the incidence of neurological impairment. Cioni et al. reported 29 immature children with PVL, most of whom later developed cerebral palsy. They found a significant correlation between visual function at 1 year of age and neurodevelopmental evaluations at 1 and 3 years of age. Multiple regression results showed that visual deficits were the most important variable related to cognitive level when compared with motor impairment and MRI. It is suggested that vision plays a key role in the early cognitive development of these pediatric patients.
Cerebral visual impairment affects all aspects of neurodevelopment, including early motor development, communication, emotion, self-care, and cognitive level. Regardless of the degree of motor impairment, individuals with cerebral visual impairment have significantly lower levels of development.
V. Prognosis and treatment of visual impairment in cerebral palsy
Richard Huo retrospectively analyzed the visual function of a group of children with cortical visual dysfunction, 58.2% of whom had cerebral palsy, and found an average improvement of 2 levels of visual function at follow-up. porro G et al. performed a 5-year longitudinal follow-up of grating visual acuity in children with cerebral palsy and found 14/16 good or moderate visual acuity improvement. Most of the visual acuity of cerebral palsy-induced amblyopia improved after treatment. Therefore, the potential for recovery of reduced visual acuity due to cerebral palsy is promising. The treatment of visual impairment in children with cerebral palsy is less reported, and the main emphasis is on oculomotor and regulatory functions, which can effectively improve visual function through treatment.
In summary, children with cerebral palsy are not only motor impaired; visual impairment affects visual afferents or visual efferents and therefore neurodevelopment. Cerebral visual impairment affects pediatric development as much as motor impairment, especially early motor development. Therefore, the examination of children with cerebral palsy should include a more detailed ophthalmologic and visual function examination to identify problems early and to develop a rehabilitation plan to promote improvement of visual function and full rehabilitation of the child.